I decided the only way to turn the completed front section would to be in a "socket". The section sits on a shoulder on the nose and is secured with a setscrew

turning ID of socket

Next up is some stock for the body of the tube. I found something that was close in ID and OD.

Boring in lathe.

Before I committed to having a overly long piece I had to cut the barrel lugs (and blocking lug for SBR)

modifying barrel (now extended) for blocking lug

After that the blocking pin preventing a FA bolt from going into battery

In socket ready to be turned

turning shoulder

Tube section shrunk on

Complete tube in lathe and tacked. Although I do not recommend welding in a lathe, it seemed the only way I could hold everything straight without building a fixture. If you do this use a TIG, If any other process cover everything with aluminum foil to keep the spatter from damaging, most important is to keep the ground as close to the work as possible and never crossing a bearing.

So true, A project like this seems to always show a need for a jig or some part to be made to protect the part in the lathe or ?. But The fun of doing it and the satisfaction of a job well done is PRICELESS